Telephone set hook-switch apparatus



April 109 i951 J. F. HOUDEK, .JR 25489723 TELEPHONE SET Hooxsw1frcH APPARATQS Filedl July 15, 1945 5 Sheets-Sheet 1 pri l0, 951 .1. F. HouDEK, JR

TELEPHONE SET HOOK-SWITCH APPARATUS 5 Sheets-Sheet 2 Filed July 13, 1945 .k O u@ w m Apri 10, E951 J. F. HQUDEK, JR 25489723 TELEPHONE SET HOOK-SWITCH APPARATUS Filed July 13, 1945 5 Sheets-Sheet 3 ffy; 7.

pri l0, 195i J. F. HOUDEK, JR

TELEPHONE SET HOOK-SWITCH APPARATUS Filed July 13, 1945 5 Sheets-Sheet 4 (Loc/1.1. BATrE/Pr sfr) April l0, 1951 J. F. HoUDEK, JR 2,548,723 TELEPHONE sm HOOK-SWITCH APPARATUS Filed July 13, 1945 5 Sheets-Sheet 5 (cor/MON nrsmr ser) r Patented Apr. 10, 1951 TELEPHONE SHET HOOK-SWITCH APPARATUS Joseph F. Houdek, Jr., Chicago, Ill., assigner to Kellogg Switchboard and Supply Company, Chicago, Ill., a corporation of Illinois Application July 13, 1945, Serial No. 604,856

3 Claims.

This invention relates to telephone sets such as are installed at subscriber stations.

Its general object it to provide an-irnproved constructional arrangement permitting use of the same basic assemblage to meet a wide variety of station requirements imposed by the varying lengths and electrical characteristics of subscriber lines and imposed by varying character of the central-cnice equipment.

A further object is to provide a telephone set of the general character set forth which includes a base assembly which, together with a cordattached hand telephone and a suitable housing,

comprises a lcomplete telephone set to which the necessary conductors `may be attached according to any one of a number of specific requirements.

One feature of the invention is that a telephone set constructed in accordance' therewith can be used alternatively as a local-battery set and as a common-battery set; that it is adapted to one use or the other according to which of two specically different induction-coil blocks is incorporated therein; and vthat the telephone set for each such use is anti-sidetone in operation.

A further feature is that the set, when adapted for common-battery use, is readily adaptable for use on lines of Widely varying lengths and electrical characteristics. According to this feature, a local resistor is so located in the circuit arrange ment oi the set that it can be included alternatively as a part of the line resistance and as a part of the resistance of the anti-sidetone ybalancing arrangement, and can be excluded from both.

Other objects and features' of the invention will appear as the description progresses. ,y

The accompanying drawings, comprising Figs. 1 to 21, show apparatus views and circuit dia-Y grams of telephone-set equipment constructed according to the invention.

Fig. l is a perspective view, generally from the front, oi av desk set incorporating the invention.

Fig. 2 is a View of the base assembly incorporated in the telephone set of Fig. 1, as seen from a point above the right rear corner thereof.

Fig. 3 is a plan view of the base assembly shown in Fig. 2, but with certain parts removed.

Figs. 3A and 3B are fragmentary views, partly in section, of certain details of construction of base block 9 of Figs. 2 and 3.

Fig. 4 is a profile view of the condenser block I3 of Fig. 2, with parts broken away to show the construction. Y

Fig. 5 is a prole view of induction coil block :I4-LB of Fig. 2,'with parts broken away to show the Vinternal construction.

Fig. 6 is a rear view of vthe telephone set of Fig. l, with the rear part of the housing broken away.

Fig. 7 is a bottom view of base block 9, showing the permanent conductors interconnecting the screw and pin terminals and the leaf ksprings mounted therein. v

Figs. 8 and 9 show how the pin-socket ter-,- minals are constructed and held in place in base block 9.l v

Figs. 10 to 12 show the construction and arrangement of hookswitch ll0 of Figs. 2, 3, .and '7.

Fig. 13 is a fragmentary View, partially in section, showing the arrangement yassembled in base block e for controlling hookswitch i0.

Figs. 14 and 15 show alternativepositions of switching links I1 and I8 respectively of Fig. 2.

Figs. 1.6 and 17 show second-and third positions of link I9 shown in position-,1 vin Fig. 2.

Fig. 18 is a circuit diagramof the Ysubset adapted for local-battery talking by the inclusion of coil block I4-LB -of Figs. 2 and- 5, and further vadapted for common-,battery signalling by the inclusion ofv a bridging retard coil 64,

Fig. 19 is a'circuit schematic of the arrangement shown in wiring-diagramA form in Fig. 18.

Fig. 20 is a Wiring diagram of the setadapted i'or rcomirion-battery talking and signalling by the inclusion of induction coil block lll-CB therein, similar physicallyto the local-battery coil block ill-LB, illustrated in Figs. 2 and 5, and further adapted to'.serve .as an automatic telephone set by being provided with a calling device TI. Y

Fig. 2l is a circuit schematic of the 4arrangement shown inw'iringl-diagramfform "in 20.

Reference isn-lade tothe co-pending applica tion of Cliliord E. Erickson `for Telephone Sets', Serial No. 594,619,'led May 19, 1945, now Patent 2,495,164 dated January 17, 1950, which illustrates the use of a base assembly as shown her-einrv at Fig. 2 with a housing ofone form to make up a des-k set as shown herein inV Fig. 1-, and' its usey with a housing of another formy to make up a wall set. y

The general arrangement amarga base assembly. Line cord 6 contains four conductors for making all required external connections to the set.

The base assembly, shown in Fig. 2, includes base plate 'i and the parts attached thereto. These attached parts include base block 9, which carries all necessary attachment terminals for the entire set; condenser block I3; coil block Ill-LB; and ringer I5. Hookswitch I0, together with its actuating parts II and I2, is received within a suitable opening in base block 9.

It has been chosen to illustrate the base assembly in Fig. 2 as adapted to local-battery operation. Accordingly, such assembly is equipped with local-battery induction-coil block lll-LB instead of with the generally similar commonbattery induction-coil block I4-CB (Figs. 20 and 21) which differs in its arrangement and connection of coil windings to the terminals; link IS) isY illustrated in its local-battery position, bee tween terminals 35 and 34; and local battery lead B2 (not used in the common-battery set) in line cord 6 is shown connected to screw terminal 35. As will hereinafter appear, the other connections to screw terminals are similar for local-battery operation and common-battery operation. fScrew terminals are carried in base block 9 as follows: screw terminals 2l to 23 for the conductors in handset cord screw terminals 23 and 30 for the line conductors contained in line cord 5; screw terminal 3| for the ground conductor in line cord 6; screw terminals 26 and 3l for flexible leads I6 attached to ringer l5; screw terminals 28 and 33, serving as attachment points for flexible leads attached to a bridging retard coil (see Fig.l 18) when a local-battery set is to be adapted for common-battery signalling; screw terminals 24 and 25, provided to enable the two-position condenser link I'I to alter the condenserv capacity in the ringer circuit; screw terminals 31|, Aprovided as one connection point for the two-position ringer link I8 which cooperates alternatively with a second screw in each of the double-screw terminals 30 and 32 (see also Fig. to enable one ringer connection to be shifted alternatively between a line conductor and ground; and screw terminals 34 to 36, which ('in the common-battery embodiment) cooperate with the three-position transmitter link I9 (see also/Figs. 16 and 17) which adapts the set for operation according to the resistanceof the line to which it is connected. Y

The base block Referring now to Fig. 3, it will be noted that condenser block I3 and coil block I 4-LB of Fig. 2 have been removed from the assembly and shown in side View in the associated Figures 4 and 5. The respective assembled positions occupied by these parts are shown in dotted outline in Fig. `3. The pin-socket terminals through which parts I3 and lli- LB attach, mechanically and electrically, to the base block 3 are exposed to View in Fig. 3.- These pin-socket terminals include the live terminals 4Ia to 4Id for condenser block I3 and thel seven terminals 43a to 43g for coil block I4-LB.

The four pin-socket terminals 42a to 42d (Figs. 2 and 3) are provided to receive a calling-device plug whenk the set is used as an automatic telephone set, as in Figs. and 21'. When the calling device is not employed, terminals a and c in group 42 are bridged by a link 20, which may be a section of Wire,v bent in the form of a staple,

(Fig. 1).

'4 inserted as shown in Fig. 2. Link 2D has been removed from the assembly as shown in Fig. 3.

The several screw terminals and pin-socket terminals mounted in base block 9, together with downwardly extending terminals of hookswitch 2B, are interconnected within the hollow back portion of the base block, as shown in Fig. 7. The interconnection is accomplished by preformed conducting strips 4l received within the prongs of the bifurcate terminal ends. The form of the bifurcate terminal ends of the screw terminals is as illustrated in Figs. 3A and 3B for screw terminal 30; the bifurcate end of the pin-socket terminals is as illustrated at 52 in Fig. 9; and the bifurcate terminals of the leaf springs in hookswitch I0 are shown at i9 in Fig. 12.

A feature of the invention is that base block 9 is so formed as to be readily molded, of an insulating plastic material, with no metal inserts Whatever. As molded, base block 9 contains openings for the three screws 40 (Fig. 3) which secure block 9 to base plate 1. Recesses 38 and 39 laterally receive handset cord 5 and line cord 6, incoming through marginal slots in housing 2 The metal fasteners customarily secured to cords such as 5 and 6 (Fig. 2) are conveniently secured under the heads of the two mounting screws 4U which lie within recesses 38 and 39.

As is indicated best by comparison of Figs. 2, 9, and 13, the base block 9 has the entire back portion recessed to form a downwardly opening cavity withn which the local interconnecting conductors 4l are supported, by the pronged terminal ends to which'theyare attached, within the confines of the base block and in spaced relation to the base plate 'l on which the block is mounted. The pronged terminal ends to which interconnecting conductor 4l attach all lie in the same general horizontal plane, except those of doublescrew terminal 31 which is mounted at a higher level to permit conductor 4'IYto pass freely above the interconnecting conductors 41 which it crosses.

Screw terminals Base block 9 has openings formed therein for receiving individually the several screw terminals 2l to 3l. Each such opening is in the form of a rectangular shaft having a width suicient to receive the downwardly extending end portions of the concerned screw terminal, but of insunicient width to permit the wider horizontal main portion of the screw terminal to pass through. The opening for receiving doublescrew terminal 3U is shown in fragmentary sectional view 3A. Fig. 3B shows that this opening is wide enoughto receive the terminal ends 53, but of insufficientwidth to receive the main horizontal portion of the screw terminal. Outwardly pointed barbs 5d (Figs. 3A and 3B) engage the under Ysurface of base block 9 to hold screw terminal 3B securely in its installed position. The material of which the screw terminal is made preferably has sufficient spring action that barbs 54 'cause a slight inward compression of terminal ends 53 as terminal 30 is being forced downwardly into its illustrated installed position, followed by an outward snap action to the illustrated locked position. Such a terminal can be readily removed by first compressing end members 53 together suiciently to clear barbs 54, followed by a withdrawal of the terminal. Similar openings, but of a reduced length,y are provided for single-screw terminals such as 2l, 22, etc. A

enligne single barb such as 54 suffices to retain a single screw terminal in place. A portion of the opening in block 9 for removably receiving singlescrew terminal 36 is shown inA Fig. 3 below the broken-away end portion of vterminal 36. All the openings for the screw terminals can be seen from below in Fig. '7, with the screw terminals in place.

Pin-socket terminals Suitable openings in base block 9 are provided for each of the pin-socket terminal groups 4l, 42, and 43. The wall of the base block is thickened at regions 55, 5S, and 51 (Fig. 9) by formations which may be described as dependent bosses. The extent of boss 56 is shown in crosssection in Fig. 9. This thickening of the wall permits a satisfactory rsupport length for the pinsocket terminals not required for the screw terminals.

All of the pin socket Yterminals may be of the same construction. Pin-socket terminal 42h of Figs. 2, 3, and 'l is shown separately in top View in Fig; 8, and is shown in Fig. 9 as seen from the side. a split tube which lies within its opening in base block 9. The top end of the tube is provided with a laterally extending positioning tab '5I formed integrally therewith. In assembled position, tab 5| lies in a positioning recess formed adjacent to the top end of the opening through part 9, thereby fixing the position of the pinsocket terminal rotationally to conform to the predetermined direction of the concerned portion of the conductor 4l (Fig. 9) which is to be received between the prongs of its bifurcate endV portion 52. End portion 52, formed. integrally with the remainder of the terminal 42h, is wider than the opening through base block 9. Partsl 5l and 52 cooperate to prevent withdrawal of the terminal from its installed position. To enable the pin-socket terminal of Figs'. 8 and 9 to be installed and secured in place, it can be formed with part 52 originally curled sufficiently to pass downwardly through the opening in the base block, following which it is flattened to `increase its width to prevent withdrawal. In the event that such a terminal requires to. be removed, this can be accomplished readily by again curling part 52 sufficiently to permit it tobe withdrawn. Alternatively, part 52 can be bent back and forth until it breaks to permit the remainder of the pin-socket terminalV to be withdrawn for replacement by a new one'. opening through which the pin-socket'terminals pass are substantially larger than the pin-socket terminal so as to permit expansion ofthe pinev socket terminal when it grippingly receives a pin terminal, and also to permit substantial lateral displacement of anypin-socket termi-nal to accommodate variations in the'relative locations of several pins which are to cooperate with a` group of the pin-socket terminals.

The hookswitch.

hookswitch to be clamped in place by a pair of" This terminal has the general form 0i"` Preferably, the` shoulder nuts 52, slotted to permit them to be' tightened and loosened -by an `ordinary screw driver. The opening containing hookswitchl is preferably provided with a removable cover (notshown) for keeping dustand other foreign particles from falling into the contacts ofthe hookswitch.

Referring to Figs. 10 to 12, the hookswitch is shown removed from the base block. It includes six leaf springs a to f supported and adjusted to make contact as shown when the handset is removed from the cradle. As will be subsequently explained, when the handset is placed on the cradle, the free end of the hookswitch is moved to the left to cause leaf springs a and b to break contact witheach other; to cause leaf springs c, d, and e to break contact with each other; and to cause leaf springs e and f to make contact. For this purpose, leaf springs b and e are interconnected by an insulating bushing,

as shown.

The leaf springs are held in assembled position by the pressure applied by two screws 6l acting to clamp the leaf springs and their illustrated apertured yinsulating plates between clamp plates 59 and 60. Plate 69 is threaded to receive screwsA 6.1which pass freely through openings in plate 59, 'as Well as through the intervening parts.

One important feature of hookswitch l0 is that each of the leaf springs is provided with a downwardly extending tab 49 having a bifurcate terminal end to receivethe concerned one of conductors lli (Fig. 7) within the cavity containedv in the hollow back portion of block 9. It is to be noted` that the side tabs of the leaf vsprings are provided in pairs, each pair being disposed at a different location along the/clamped portion of the springs to enable the concerned conductors di (Fig. 7) to make contact with them when arrangedY in the orderly manner shown in Fig; 7. v

As seen in Figs. 'l and 12, the opening in base block 9 which receives hookswitch I0 is provided with a sup-porting bridge 48 on which hookswitch lrests at a point just forward of the front pair` of downwardlyk extending terminal tabs. This bridge is useful in locating the hookswitch horizontally in the desired locationY prior to the tightening of retaining nuts 62.

H oo'lcswitch control The arrangement for operating hookswitch l0 between its illustrated talking position and its alternate normal position (with a, bl and c, d, e.

open, and e, f closed) is illustrated'best in Fig. 13,Y examined in conjunction with Figs. 2, 3, and

6. A transverse opening is provided below the n ing means. The end of the generally vertical arm of bell crank il is arranged so as'to engage the free end of leaf spring bof hookswitch, Il), on

assembly of the parts, and displace itJslightly toward its normal (handset-on) position so'as to` urge plunger i2 upwardly with the shoulderthereof snugly in contact with the surrounding1 under surface of base` block 9. The hookswitch is then in its illustrated alternate (handset-olf) condition.

When. the housing is finally assembled, and handset 4 is placed in its cradle as shown in Figs. l and 6, plunger I in the housing (in longitudinal alignment with plunger I2 carried by the base) is depressed under the weight of the handset, thereby dep-ressing plunger I2 and rotating bell crank II about pivot pin II. The free end of the hookswitch is thereby moved to the left as seen in Fig. 13, and upwardly as seen in Fig. 10, to bring the hookswitch to its normal position. The hookswitch returns to its illustrated alternate position responsive to any subsequent removal of the handset.

Conductors 47 As shown best in Fig. '1, it will be noted that each interconnecting conductor 41 comprises a preformed strip, such as may be punch-formed from sheet material. In practice, all of the conductors 41 may be punch-formed from a single sheet about the size and shape of base block 3 and left connected together in the form of a grid until vafter they have been placed in position. Thereupon, the bifurcate terminal portions of the depending terminal members, such as 53 of Fig. 3B, 52 of Fig. 9 and43 of Fig. l2, can be crimped inwardly to mechanically` retainconductors 41 in place. Each concerned terminal connection is preferably soldered to enhance its permanency. The grid may be cut through before or after the soldering operation to divide it into the separate conductorsY 41 shown in Fig. 7. The single cross-over conductor 41 may comprise a piece of wire secured between screw terminals 3l and 31 `as shown.

Condenser cmd coil blocks Upon referring to Figs. 4 and 5 in connection with Figs. 2 and 3, it will be observed that the condenser and coil blocks I3 and I4--LB are of similar construction except that condenser block I3is somewhat Vlonger because of the increased volume othe enclosed condensers as compared to -the induction coil. Each block is in the form ofV a/two-piece container, the lower section ot which is provided with pin terminals shown at 44 for condenser block I3 and at 45 for coil block Ill-LB. The lower portion of the block is provided with anl overhanging shelf through which the pin terminals 44 or 45 protrude. The protruding endsof these terminals cooperate with pin-socket terminals 4I or 43 as the case may be. Condenser` block I3 has rive terminals for cooperation respectively with pin-socket terminals a to ein group 4|, while coil block I4-LB has seven pin terminalsior cooperation respectively with pin sockets a to g of group 43. The inner end of each pin 44 or 45 is formed as shown for one suchpin 44 in Fig. 4 to receive one or more internal terminal conductors. Preferably, after thecondenser assembly, or the induction coil, as thecase may be, has been placed in the lower section ofthe concerned one of the two blocks, and has had its terminal leads connected to the inner end of the terminal pins, the block is filled with an insulating compound surrounding the condenserpr coil, following which the upper portionof the'bloclris assembled and is secured in place as by cement. The finished block (I3 or I4LB) is thus sealed against the entrance of moisture into the electrical apparatus contained.

therein. ,As shownbest in Fig. 2, observed in conjunction with Figs. @and 5, each of theblocks I3 and I4-LB lies partly opposite the forwardedge of base block 9 and partly overhangs the base block. Either such block is placed in assembled position by bringing it vertically downward into the position shown, with its pins (44 or 45) entering the pin sockets (4I or 43 as the case may be). It will be observed that the lefthand portion of base block 9 is narrower from front to rear than the remainder thereof so as to accommodate the somewhat greater length of condenser block I3.

The pin terminals (44 or 45) of either of the blocks under discussion are rather widely spaced to conform with the spacing of the concerned pin-socket terminals 4I or 43 (Fig. 3). As a result, each of the two blocks is held reliablyin place by the gripping action of the pin socketv on its terminal pins, rendering additional securing means unnecessary. A special feature of this arrangement is that when the base assembly is incorporated in the complete set, the housing 2 (Figs. l and 6) serves to retain blocks I3 and I4-LB in place in the event that they should tend to be jarred out of position during shipment in an upside-down condition, as may occur. This feature results from the disclosed location of blocks I3 and I4-LB parallel to the longer sides of the base plate 1 and below the abutments formed in the housing 2 where the enlarged base portion thereof gives way to the narrower pedestal portion which terminates in the handset cradle.

Upon referring to Fig. 18, for example, it is seen that condenser block I3 contains singlesection condenser 62 employed in the talking' circuit and double-section condenser 63 employed in the ringer circuit, and that block I4--LB' contains a local-battery induction coil having windings 14 to 11, which encircle the central leg of a common iron core I4 (Fig. 5), in accordance with the usual practice.

Local-battery set Fig. 18 shows a wiring diagram of the dis-A n battery telephone set. The apparatus shown in Fig. 18 is generally the apparatus shown in Fig. 2. The handset 4 is connected to the base assembly by cord 5, and the terminal block' IS--T is connected thereto by line cord ii. A local battery IB-B is connected to the upper and lower terminals of block I8-T, between conductors LI and B2` in line cord 6, to supply energizing current for transmitter T in handset 4. Additionally, retard coil 64 is connected between terminals 28 and 33 to equip the set for commonbattery signaling, as will be discussed herein-l after.

As previously noted, the local-battery set shown in Figs. 18 and 19 is equipped for common-battery signaling by retard coil 54 being bridged between terminals 33 and 28. This retard coil has not been shown in the mechanical portion of the drawings. In practice, it may be mounted on the base assembly by a bracket secured under the screw of spare terminal 21.

In Fig. 18 the base block 9 and'other parts are shown in top View as they appear in Figs. 2 and 3. Accordingly, the interconnecting con ductors 41 of Fig. 1 are invisible because contained in the hollow back portion of the base block. This fact is indicated in Fig. 18 by show-A ing the several conductors 41 as alternately; heavy an light chained lines. These conduc-i tors form the permanent wiring of the set and are shown extending to their respective terminals in the normal manner. The other conductors (those in cords and 6, ringer conductors I6, and retard-coil conductors 65) constitute the removably connected conductors. They are consequently shown terminating at base block 9 in arrow-heads to assist in relating the wiring diagram to the physical equipment which it represents. Similarly, the pin-terminals 4(groups i4 and 45) and links I8 to 29 are provided with arrow-heads at the points where they repectively attach to fixed terminals of base block 9.

Fig. 19 shows the apparatus of Fig. 18 rearranged in circuit-schematic form to enable the circuit arrangement of the local-battery set te be understood more readily. The several conductors 41, comprising the permanent wiring of the set, are here shown as heavy solid lines, to more readily dierentiate them from the removably connected conductors, links, and pin terminals.

As previously noted, both the local-battery set and the common-battery set are arranged for what is commonly termed anti-sidetone operation. To this end, the local-battery induction coil contained in block Ill-LB is provided with a balance winding 'l5 and an artiiicial-line resistor l, in addition to primary winding 'il and secondary winding la. Windings '1li to l5 are bridged across conductors Ll and L2 in series with condenser 52 in block i3 and hookswitch springs |90, lud, and Ille, in talking position. This bridge further includes pin terminals 55e, 45h, 55d, and 55a of block lll-LB; pin terminals mlb and Alle of block I3; and link 2l! which connects terminals a and c in calling-device group 42 (Figs. 3, 7, and 18).

Receiver R of the handset is connected between the junction orA coil windings l5 and 'M and conductor Ll in line cord 8, through hookswitch springs 19a and Mib, and lcd and lile. The receiver R is thus in bridge of the artificial-line resistor T6 and its supply coil l5, whereby the receiver RE carries no current during transmission from the illustrated set so long as the line to which conductors Ll and L2 extends is balanced by the artificial-line resistor l5, according tothe relative number of-turns of secondary windings 'M and l5. To the extent that a perfect balance does not exist, current flows through the receiver R during transmission from the local set, as is common with commercially produced telephone sets of this so-called antisidetone type.

In the talking condition illustrated in Fig. 19, current is ilowing through the transmitter T from local battery lli-B. The supply path may be considered as over conductor B2 in line cord B, through primary winding 'I7 in the inductioncoil block lll-LB, and transmitter conductor TR in cord 5. The return path is then the one over common conductor C in cord 5, contact springs ld and 19e of the hookswitch, and line conductor LI in cord 8. It will be noted that the supply path to transmitter T further includes screw terminals 36, pin terminals 45g and 55e of block lli-LB, screw terminal 35, three-position link i9 in its illustrated rst position, and screw terminals 34 and 2l. In the local-battery set, linkl I9 must be used invariably in its first position shown in Figs. 18 and 19, the other two positions being used only in the common-battery set, to be subsequently described in more detail.v

With retard coil 64 incorporated in the circuit as shown in Figs. 18 and 19, closure of the hookswitch contacts lllc, 19d, and ice, responsive to the removal of the handset, bridges the retard coil across line conductors Ll and L2 through link 2-0. A direct-current signalling path is thus closed in the manner common to common-battery systems. The principal utility for this arrangement is in a common-battery system on lines which are so long, or the resistance is otherwise so great,v that -a satisfactory flow of transmitter Vcurrent cannot be obtained thereover. The common-battery signalling feature is retained, but thev transmitter is supplied with current from the local battery IS-B as previously pointed out. However, it is contemplated that most local-battery sets will not equipped with coil 94, but will employ magneto signalling by means of a hand generator connected to the line through leads 91.

When common-battery signalling is employed, it will be noted that condenser 62, being interposed between coil winding 'M and conductor L2, prevents direct current from flowing through coil windings '14 and 'i5 and through receiver R. The path of the signalling direct current is thus l coni-ined to the bridge through retard coil E4.

The condenser 52 is also of utility when the local-battery yset of Figs. 18 and 19 is used (without retard coil 55) in a system employing magneto signalling. It prevents stray direct` currents (furnished Vfor example through certain specialr cordcircuits in the exchange) from owing through the windings .of the induction coil and the receiver, thereby avoiding such harmful eects as these currents might produce in apparatus designed to operate free therefrom. Additionally, condenser 62 limits the flow of the relatively low-frequency ringing currents from the central oice or from other subscriber stations on the same line, `thereby,permitting a de-` sired subscriber station to be signalled notwithstanding the fact that the hand telephone may be removed atone or more other stations on a party line. s' f 1 Contacts Illa and Illb have a 'common purpose in all contemplated `circuit embodiments, both local-battery and common-battery. YSuch contacts are preferably ladjusted to engage last when the handset is removed vand todisengage rst when the handset is replaced. These contacts thus immediately open-circuit receiver R' when the handset is replaced to prevent clicks` in the receiver incident to the subsequent opening of the transmitter circuit at rvcontacts llld and Ille. transient condition tending to cause a clicking in theA receiver R incident to the closure. of the transmitter circuit, or of the signalling circuit,

at contacts 19d and Ille are given time to sub- Y side before contacts lila and |01) place the receiver R in circuit. l

When the local-battery set of Figs.v 18 and 19 is equipped as shown for common-battery signalling, hookswitch contacts I lla and lb prevent lower terminal of ringer l5 is connected to' When the receiver is removed, vtheY ground over conductor G in line cord E. This is the ringer connection employed for so-called divided ringing, used when the ringers at certain subscriber stations on a party line are connected between one line conductor and ground, and the ringers at the other stations are connected between the opposite line conductor and ground. 'Ihe line conductors are connected in what may be considered the normal way to the line terminals of strip IB-T at one group of stations on party lines and are connected in what may be termed the reverse way to the line terminals of strips IB-T at the other stations on the line, whereby the application of ringing current at the central office to one line conductor or the other affects the ringers at one group of stations or the other.

When bridged ringing is desired link I8 is shifted to its second position (Fig. wherein it connects screw terminal 3| with screw terminal 30 instead of with screw terminal 32, thereby bridging the ringer circuit across conductors LI and L2.

With condenser link I'I in its illlustrated irst position, both sections of condenser 62' are employed in the ringer circuit to provide full condenser capacity where required. When only the capacity of the upper section of condenser 63 is required, link I1 is shifted to its second position (Fig. 14), wherein it does not bridge screw terminals 24 and 25. It may be noted that systems employing selective signalling on party lines by the use of ringing currents of separate frequencies and tuned ringers I5, two condenser capacities are customarily provided, one or another of which is used at a subscriber station according to vthe signalling frequency assigned thereto. The disclosed switching arrangement involving the two-section condenser 63 and link II enables a telephone set incorporating the illustrated base block 9 and condenser block I3 to be readily adapted for use at any one of a large number of subscriber stations. In those cases requiring condenser capacities not obtainable with condenser block I3, such block can be readily withdrawn from its installed location and replaced with a similar condenser block containing a condenser 63 having sections of a desired other capacity.

When the local-battery set of Figs. 18 and 19 is equipped with retard coil 64 to adapt it for common-battery signalling, it serves as an automatic telephone set by merely removing link to enable a calling device to be plugged in, as shown in Fig. 20 for the common-battery set.

Common-battery set In Figs. 20 and 21, the basic arrangement is shown equipped as a common-battery set (instead of as a local-battery set according to Figs. 18 and 19) by being supplied with common-battery induction-coil block III-,CB in place of induction-coil block I 4-LB used in the local-battery set of Figs. 18 and 19. Block lli-CB may have the same physical dimensions as block Ill-LB, and is provided with a group of pin terminals 45', comprising terminals a to g which tit respectively into the same pin-socket terminals a to y of group 43, occupied in Fig. 18 by the pin terminals 45 of block I4-LB.

In the common-battery modication shown in Figs. 20 and 21, local battery I8-B of Fig. 18 is omitted and the unneeded conductor B2 in line cord 6 is disconnected from screw terminal 35 and left unused. Moreover, retard coil 64 of Figs. 18 and 19 is never required in the common- 12 battery set, as it is used only in the local-battery set, to adapt it for common-battery signalling.

The common-battery set shown in Fig. 20 is further illustrated as adapted for use as an automatic telephone set. This adaptation is accomplished by removing link 2li of Figs. 3, 18, and 19, and replacing the four-pin calling-device plug 68 in the pin-socket terminals 42a to 42d as indicated in Fig. 20. This plug is connected, by the four-conductor cord 'I|J, to calling device "II, which may be mounted in housing 2 of Fig. 1 in the position occupied therein by the removable blank 3.

The common-battery set, shown in wiringdiagram form in Fig. 20, is shown in circuitschematic form in Fig. 21, to enable the circuit arrangement thereof to be more readily understood. Upon reference to Fig. 21, it will be observed that the circuit elements of the commonbattery set are related to each other in the same way that they are in the local-battery set with the exception that the common-battery coil block I--CB is provided with an induction coil having a specifically different arrangement of coil windings which are connected respectively to the concerned pin terminals 45 to provide the different circuit arrangement required for the commonbattery set. A comparison of Figs. 19 and 2l shows that condenser 62 in condenser block I3 is connected at a point between line conductor LI and the repeating-coil windings in Fig. 21, whereas it is connected on the opposite side of the repeating-coil windings in Fig. 19, between such windings and conductor L2. This shift in the location of the condenser is accomplished readily, in the physical arrangement disclosed, by merely connecting the pin terminals of each of the blocks I4--LB and I4-CB internally according to the desired circuit arrangement. It is made possible by the fact that both terminals of condenser 62 are carried to pin-socket terminals engaged by pins of whichever one of the coil blocks is inserted. The respective correspondence between the pin terminals of block Ill-CB and block l4-LB are shown by the assignment of the same reference characters in both cases, except that the numerical part of the reference character assigned to any pin terminal of block Ici-CB is primed.

A further shift between the local-battery set and the common-battery set is in the relative circuit positions occupied by the transmitter and the receiver. In the local-battery set, the transmitter is in a local circuit (including winding I'I), while the receiver is in the local circuit in the common-battery set, including winding 'I1'. In the common-battery set, the transmitter is connected by way of lead TR and link I9 to a point between the serially related line windings and 14') whereas the receiver employs that circuit position in the local-battery set.

With the hookswitch in its talking position illustrated in Figs. 20 and 21, transmitter T is in a direct-current bridge across conductors LI and L2, which (with calling device Il in use and with link I9 in the position shown) includes impulse contacts 'I2 of the calling device, line winding 'I4' within induction-coil block I lI-CB, noninductive resistance winding 13, link I9, transmitter T, common cord conductor C, and hookswitch contacts Id and Ille.

Transmitter T is shunted by the anti-sidetone arrangement (balance winding 'I5' and articialline winding 16') in series with condenser 62, which blocks the flow of direct current through windings I5 and 16', confining all of it to the path through transmitter T. This shunt path includes terminals d, b, and c of group 45T, terminals e and b of ygroup 44, and hookswitch contacts Ic and I Ild.

Receiver R is included in a local circuit with secondary winding 'Il'. On one side, this local circuit includes terminal pin .57 of block I4--CB and hookswitch elements Illa and Ilb. On the other side, it includes coil-block pin 450 and hookswitch elements IIlc and IIld.

When transmitter T is operated to vary the current ow therethrough, a voltage variation Vis thereby produced across line conductors LI and L2 in the well understood manner. Articiahline resistor 15.', being arranged to gen erally balance the impedance oi the line to which the subset is connected, in, view of the turn ratio chosen for coils 75 and '14', permits suiiicient current to flow through winding I5 and condenser 62 to substantially balance the variations in current flow through line winding 14', thereby preventing the local receiver winding I'I from being affected, except to the extent of such unbalanceas exists. When incoming voice currents arrive over conductors LI and L2, all such currents pass through line winding 'M' and resistor I8. Fromthis point', they divide, a part of them flowing through transmitter T and a part of them continuing through windings l5 and I6 and condenser 62 to the other side of the talking circuit. At this time, the current flow through windings 'I5' and I4 is in aiding relationship, whereby local winding I'I is influenced to drive current through receiver R, in the manner common to anti-sidetone substation circuits of the character illustrated.

When, following removal of the handset, the usual dial (not shown) of calling device 'II is turned off-normal incident to the setting thereof for the transmission of a desired number of impulses (interruptions of contacts l2) on the return movement, shunt contacts 'I3 close and remain closed until the dial returns to normal position, following the delivery of the last impulse of the series. The inner one of contacts 'I3 is connected to the lower line conductor, as extended through contacts 'I2 to the lower terminal of winding 'I4'. The outer one of contacts 'I3 is connected, through pin terminal l58d and pinsocket terminal 42d to the upper talking conductor, by way of hookswitch contacts IIld and Ille. Accordingly, the substation devices normally in circuit across the talking conductors are shunted out when contacts 13 close together. The middle one of the three shunt contacts 'I3 is connected to receiver lead RE through pin terminals 68h and socket terminal 42h.

The outer and middle contacts 'I3 close together first as the previously mentioned dial is turned from its normal condition, thereby rst shunting the receiver R. Accordingly, the current changes incident to the principal shunting operation are prevented from affecting the receiver R. On the completion of the return movement of the dial of calling device 'II, the inner and middle ones of the shunt contacts I3 open rst, thereby reestablishing normal conditions in the telephone set prior to the opening of the middle and outer contacts 'I3 to again place the receiver R effectively in circuit.

The common-battery set is illustrated in Figs. and 21 with the three-position link I9 therein placed in its first position between screw terminals 34 and 35. This is the position intended when the -lne leading to the substation is a relatively short, or low-resistance, line. With link I9 in its illustrated first position, resistance winding I8 is in circuit with the relatively short line. This has two useful purposes. First, it increases the effective natural line resistance to a point-toward the assumed resistance value for which the articial-line resistor 'I5' is calculated, thereby helping to bring the short line up toward a balanced condition for better anti-sidetone operation. Second, resistor 'I8 reduces the current now through transmitter T, thereby decreasingits otherwise undesirably high output, and also materially increasing its otherwise short useful life.

When the common battery set of Figs. 20 and 2l is to be used on a line/of medium length, link I9 is then transferred to its second or intermedi# ate position shown in Fig. 16. In this position, it joins screw terminals 34, 35, and 36 together in common, thereby eliminating resistor I8 from the circuit. The articialline of the set is preferably designed to give the best anti-sidetone performance when'the telephone set is connected to a line of medium length without artificial resistance added thereto.

When the telephone set of Figs. 20 and 21 is to be used on a long line, link I9.-is transferred to its third position las shown in Fig. 17. It then interconnects screw terminals'34 and 36 and is out of contact entirely with screw terminal 35. In this position of link I9, resistor 'I8 is entirely out of the line circuit over which transmitter T is supplied with talking current, and iseiectively in series with artificial-line resistor 1B', adding `its resistance to the resistance of the latter. The

thus increased artificial-line resistance enables the circuit to perform more efficiently as an yantisidetone circuit, and as an eflicient transmitting and receiving circuit, in conjunction with the long line to which the set is connected.

In the common-battery set of Figs. 20 and 21, condenser link I 'I and ringer link I8 are'shiftable between their illustrated `and alternate positions for the purposes set forth in connection with the local-battery set of Figs. 18 and 19.

Upon referring to Figs. '7, 18, and 20, it will be observed that screw terminal 21 has no conductor connected thereto. This spare terminal is provided in base block 9 to for-m a convenient connection point for circuit arrangements lwhich may be considered special, as for example circuit arrangements employing a cold-cathode discharge tube in circuit with ringer I5, as when inductive disturbances are to be minimized on party lines employing divided ringing.

I claim:

1. A telephone substation set including a terminal block having an upstanding wall rising above the general level thereof and at least partially defining an opening therein having a generally oblong cross section, there being a wide gap in said wall at one side of the opening adjacent one end thereof, the wall portion opposed to -the wide gap being provided with slots compriswith the underside of the block to limit upward movement ofthe plunger, a pivot carried by the block, a 4two-armed lever supported on the pivot with-one arm underlying the plunger and other arm operatively associated with the hookswitch,

said lever having a downwardly facing transverse vpivot-receiving channel formed therein at the `junction of said arms which denes its location onthe pivot, the parts being so related that assembling the hookswitch with the block, following the assembly of the plunger and lever therewith, holds the lever against vertical displacement'with respect to the pivot and holds the plunger at its uppermost position with its Yshoulder portion in contact with the block.

3. In a telephone substation set, a mounting block, a hookswitch and means for assembling it with the block, a control plunger extending up- 'wardly through an opening in the block and having means Xed therewith cooperating with the block to limit upward movement of the plunger, a pivot pin, the block having an upwardly opening slot formed therein Within which the pivot pin rests, a two-armed lever resting on the pivot pin with one arm underlying the plunger and the other arm operatively associated with the hookswitch, said lever having a downwardly facing transverse pivot-receiving channel formed therein 'which serves to dene its location on the pivot pin, the parts being so related that assembling the hookswitch with the block, following the assembly of the pivot pin plunger, and lever 16 therewith (a) holds the pivot pin against vertlcal displacement from its assembled position in its, slot, (b) holds the lever against vertical displacement with respect to the pivot, and (c) holds the plunger in its uppermost position.

JOSEPH F. HOUDEK, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,912,653 Olson June 6, 1933 1,919,314 Wigan July 25, 1933 1,936,245 Burke Nov. 21, 1933 2,008,283 King July 16, 1935 2,008,387 Lum July 16, 1935 2,066,876 Carpenter Jan. 5, 1937 2,199,219 Edwards et al Apr. 30, 1940 2,214,259 Pyle Sept. 10, 1940 2,226,734 McLarn Dec. 31, 1940 2,279,713 McLarn Apr. 14, 1942 2,291,808 Henning Aug. 4, 1942 2,314,225 Leece Mar. 16, 1943 2,333,299 Deakin Nov. 2, 1943 2,351,459 Shann June 13, 1944 2,355,481 McLarn Dec. 19, 1944 2,369,541 DelCamp Feb. 13, 1945 2,375,681 Obergfell May 8, 1945 2,495,164 Erickson Jan. 17, 1950 

